Power and time controlled high frequency heating appliance

ABSTRACT

PCT No. PCT/JP82/00149 Sec. 371 Date Dec. 20, 1983 Sec. 102(e) Date Dec. 20, 1983 PCT Filed Apr. 30, 1982 PCT Pub. No. WO83/03889 PCT Pub. Date Nov. 10, 1983.A high frequency heating appliance has a control circuit including a microcomputer wherein the number of input keys for entering the kind of heating load as well as the capacity of a ROM in the microcomputer are minimized by establishing a series of weight brackets substantially corresponding to the approximate usual weight ranges of Cornish hen, chicken, turkey, etc. to determine heating output and time based upon the kind and weight of heating load where beef and poultry are grouped into major classes and Cornish hen, chicken, turkey, etc. are grouped into sub-classes.

This application is a continuation of now abandoned application Ser. No.574,091, filed Dec. 20, 1983 now abandoned.

BACKGROUND OF THE INVENTION

A high frequency output is generally selected based upon the kind ofheating load in carrying out high frequency heating and cooking. Inother words, the high frequency output selected is dependent upon theconstituent materials or substances of the heating load. In addition,cooking time is determined by the high frequency output selected and theweight of the heating load. Therefore, while preparing the heating loadand consulting a cookbook, the user may select, calculate or determinethe high frequency output and heating time in view of the kind andweight of the heating load. The cookbook generally discusses a fullrange of high frequency outputs and cooking times appropriate to all ofthe different kinds and weights of the heating loads which have beenderived from preliminary or well established experiments. It iscustomary practice to enter those appropriate high frequency outputs andcooking times on a keyboard of the appliance. The conventional appliancerequires a very complicated procedure and results in an increasedpossibility of faulty operation and inconvenience in use.

To accommodate a variety of different kinds of heating loads, a fullrange of high frequency outputs and cooking times, a microcomputer isprogrammed to permit all possible combinations of high frequency outputsand heating times to be established. As a result, the capacity of an ROMin the microcomputer must be very large.

A sample is illustrated in FIG. 1 which shows some examples of poultryoften cooked in American homes. There are three kinds of poultry whichare widely cooked in American homes: Cornish hen, chicken and turkey. Itis appreciated that the high frequency outputs and heating times whichare necessary to cook those kinds of poultry are as follows:

    ______________________________________                                        Cornish hen 700 W 7 min/0.45 kg (FIG. 1A)                                     Chicken     700 W 6 min/0.45 kg (FIG. 1B)                                     Turkey      490 W 5 min/0.45 kg (FIG. 1C)                                     ______________________________________                                    

The relationships among the weight of the heating load, the heating timeand the high frequency output in those cases are depicted in FIGS. 1A,1B and 1C. Having consulting a cookbook beginning with the major classesof heating loads (in the example given, fowl) and then the sub-classesthereof (in the example given, Cornish hen, chicken and turkey), theuser of the conventional appliance finds the optimum value of highfrequency output and that of heating time from the book and introducesthese values through high frequency output setting pads and heating timesetting pads. Furthermore, the user should calculate the heating timesetting by multiplying the weight of the heating load by a unit time asshown in the book. In the conventional method, it is impossible tointroduce high frequency output and heating time settings withoutfollowing a complex procedure. The user also feels the inconvenience inuse.

An improved high frequency heating appliance of which a flow chart isillustrated in FIG. 2 has been suggested. The heating load is groupedinto major classes and subclasses as follows:

    ______________________________________                                        Major class 1 . . . beef                                                                  2 . . . pork                                                                  3 . . . poultry                                                               Sub-class    3-1 . . . Cornish hen                                                         3-2 . . . Chicken                                                             3-3 . . . Turkey                                     ______________________________________                                    

When it is desired to effect high frequency heating on the sub-class"turkey", "major class key 1" characteristic of poultry, "sub-class key3" characteristic of turkey and weight keys characteristic of a weight(w) are sequentially pressed. As a result, the heating time is computedand the high frequency output is selected automatically to carry outautomated heating processes.

In the above conventional method, because of no linear relationshipbetween weight and optimum cooking time, there are established severalweight brackets having its unique constants assigned thereto assureapproximate values of heating time. The weight brackets are usuallyequally spaced and, for example, every 2 kg against a maximum of 6 kg. Atotal of 18 constants determinative of weight-to-time relationship a₁,a₁₂, a₁₃, a₂ . . . a₅₃, b₁, b₁₂ . . . b₅₂ are required since the sameweight brackets apply to the sub-class. A greater number of the majorclasses or sub-classes would cause a remarkable increase in the numberof the constants and therefore the needed capacity of an ROM containedin a microcomputer.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a highfrequency heating appliance which avoids the inconveniences that havebeen felt in use as well as undue consumption of a limited capacity of aROM.

In essence, the weight of a heating load has a limited range mainlydetermined by the kind of the heating load for cooking purposes. Usingthe example of poultry as given above, a Cornish hen has a weightsubstantially between 0.15 and 0.7 kg, chicken within a range of 0.7 to1.5 kg and turkey within a range of 1.5 to 5.8 kg. The present inventionrelies upon these findings. As noted earlier, the heating load has itsunique weight range primarily depending upon the sub-class thereof. Inother words, the kind of heating load is suggested predominantly by theweight thereof when determined. The optimum amount of heating time isdecided primarily and automatically as long as the weight and kind ofthe heating load are already known. The optimum amount of high frequencyoutput is dependent upon the constituent materials or substances of theheating load and in order works upon the kind (subclass) of the heatingload.

Therefore, weight brackets of the heating loads, one of predominantfactors of determining heating output and time, as stored in a programin a microcomputer, are brought into agreement with usual weight rangesof, for example, poultry covering Cornish hen, chicken and turkey. Aselected one of heating outputs is preset for each of the weightbrackets which correspond to the major classes of the heating load.Moreover, the heating time T is determined from a linear relationshipT=aw+b where a and b are constants and w is the weight.

In other words, the high frequency output and the heating time aredetermined automatically predominantly by specifying the major class andthe weight of the heating load, so that heating is effected with theoptimum high frequency output and the heating time which are both mostsuitable for the sub-class of the heating load.

As long as the above concept of programming of the microcomputer ismaintained the user may conduct cooking operation at the high frequencyoutput and heating time most suitable for the sub-class of the heatingload, merely by selecting the major classes of the heating loadgenerally known to the public and setting the weight of the heating load(i.e, without the need to select the high frequency output and theheating time or retrieve the subclass of the heating load). The presentappliance is therefore very easy to operate and convenient to usewithout the need to consult the cook book.

As compared with the conventional appliance which requires a parallelcombination of high frequency output and heating time in a storedprogram in a microcomputer, the present appliance requires only a seriescombination of these two factors in programming the microcomputer andpermits the use of a cost-saving microcomputer with a decreasedrequirement for ROM capacity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B and 1C are graphic representations of the relationshipamong weight of poultry, heating output and heating time as viewed in aconventional high frequency heating appliance;

FIG. 2 is a flow chart for explaining a control method in the aboveillustrated appliance;

FIG. 3 graphically illustrates contents of a ROM in a microcomputer;

FIG. 4 is a cross sectional front view of a high frequency heatingappliance according to an embodiment the present invention;

FIG. 5 is a perspective view of the appearance of the appliance as shownin FIG. 4;

FIG. 6 is a circuit diagram of a control circuit in the same appliance;

FIG. 7 is a flow chart for explaining a control method in the appliance;

FIG. 8 is a graphic illustration of part of contents of a ROM in amicrocomputer; and

FIG. 9 is a graph showing the relationship among weight of poultry meat,heating output and heating time in the appliance.

DETAILED DESCRIPTION OF THE INVENTION

A high frequency heating appliance according to an embodiment of thepresent invention is shown referring to FIGS. 4 to 6. A high frequencyoscillator 1 of the design that provides microwave oscillation at 2450MHz is coupled via a metal-made waveguide 2 and an antenna 3. Highfrequency waves from the high frequency oscillator 1 is directed intothe waveguide 2 and radiated toward the interior of a heating chamber 4after traveling through the waveguide 2. The high frequency waves effectdielectric heating on food 5 from inside while being absorbed by thefood 5 mounted within the heating chamber 4. The high frequencyoscillator 1 is subject to self-heating due to its internal loss and istherefore cooled by a blower fan 6 to prevent faulty operation duringoscillation. Having cooled the high frequency oscillator 1, air fed viathe blower fan passes through perforations 7 in a wall of the heatingchamber 4 and enters the heating chamber 4. The air in the heatingchamber 4 traverses perforations 8 in a wall of the heating chamber 4while carrying steam generated from the food 5 during high frequencyheating. Further, the air is discharged to the exterior of the highfrequency heating appliance after traveling through the heating chamber4 and a drain guide 9 communicating between the interior and exterior ofthe high frequency heating appliance.

A control panel 10 as shown in FIG. 5 carries a keyboard 12 including aplurality of key pads 11 manually operable by the user for introducingheating output, heating time and heating mode settings and displayelements 13 such as LEDs and fluorescent display tubes for displayingthe heating output, time and mode settings. A freely openable andclosable door 14 provides access to the heating chamber 4 for the food5. A control circuit of the high frequency heating appliance will now bedescribed by reference to FIG. 6.

The high frequency heating appliance is usually plugged into a plugreceptacle in a house for supplying power supply via a power plug. Oneend 15 of the power plug is connected to a open 16 which will fuse inresponse to operation of a short switch for preventing leakage of asubstantial amount of microwaves if any electric components of the highfrequency heating appliance is shortcircuited or grounded or aninterlock as described below becomes melted. Further, the interlock 17whose contact is opened and closed upon opening and closing movement ofthe door 14 is connected to the fuse 16. The interlock 17 is alsoconnected to relay 19 which is switched on to initiate heating inresponse to a heating start command from a microcomputer 18 and switchedoff in response to an end or halt command from the same. The relay 19 isconnected to a second interlock 20 whose contact is opened and closedupon movement of the door 14 for provision of doubled safeguard. Theinterlock 20 is connected to a primary winding 22 of a high voltagetransformer 21. Connected across the primary winding 22 of the highvoltage transformer 21 are the cooling fan 6 and the above mentionedshort switch 23 which works to render the whole of the circuitinoperable when the interlock 17 or 20 becomes melted. The remaining end24 of the power plug is connected directly to the primary winding 22 ofthe high voltage transformer 21. An AC power input to the high voltagetransformer 21 is boosted into a high voltage power output throughoperation of the high voltage transformer 21. The resultant high voltagepower output is multiplied and rectified into a high voltage DC poweroutput through a voltage multiplier and rectifier composed of a highvoltage capacitor 25 and a high voltage diode 26. The high voltage DCpower output is fed to the high frequency oscillator 1 via a highvoltage switch 27 switchable in a given cycle, to thereby permit theamount of the high frequency output to be variable. The high voltage DCpower output supplied to the high frequency oscillator 1 is convertedinto high frequency radiations in the high frequency oscillator 1 andthe radiations are delivered from the antenna 3. The high frequencywaves serve to heat the food 5 in the above described manner.

The high voltage transformer 21 further includes a heater winding 28 anda biquadratic winding 29, with the heater winding 28 leading to a heater30 of the high frequency oscillator 1 for heating the heater. Thefunction of the biquadratic winding 29 is to find that the door 14 hasbeen opened in the course of heating and the interlocks 17 and 20 havebeen switched off to interrupt AC power supply to the high voltagetransformer 21 and to inform the microcomputer 18 of this finding andeventually deenergize the relay 19. It is noted that the high voltageswitch 27 is switched on and off at the given interval in response tocommands from the microcomputer 18 when heating output is set upon theuser's actuation of the output setting key.

The operation of the above construction will be described below.

The microcomputer 18 plays an important role in the whole of the controlcircuit. The primary function of the microcomputer 18 is to controlperipheral circuits, analyze and calculate information from theperipheral circuits and then control the peripheral circuits accordingto the results of such analysis and calculation. The microcomputer 18has input terminals 31 for receipt of information characteristic ofselected ones of heating output, time and modes as introduced via thekeyboard 12, a cooking interruption command from the biquadratic winding29 of the high voltage transformer 21, etc.; an accumulator 32 fortemporarily storing the commands, the information, etc. for comparisonwith data contained in a ROM area stated below, transmission into a RAMor a central processing unit and so forth; the ROM 33 for storing all ofthe commands and information necessary for controlling the whole system;the RAM 34 for storing the information and data fed from the inputterminals 31; the central processing unit 35 for analyzing andcalculating the information, data and various commands; and outputterminals 36 for delivering output signals for controlling theperipheral circuits according to the resultant data.

The output terminals 36 of the microcomputer 18 feed the output signalsto the input terminals 37 on the keyboard 12 so that output signals willbe available at the keypads 11 on the keyboard 12. A signal received byan input terminal 31 is temporarily loaded into the accumulator 32 viathe input terminals 31 of the microcomputer 18 for subsequent comparisonwith the data in the ROM 33, transmission to the RAM 34 or the centralprocessing unit 35 and calculation in the central processing unit 35. Ifthe case permits, signals resulting from the calculation are transferredfrom the output terminal 36 to the peripheral circuits such as thedisplay 13, the relay 19 and the high voltage switch 27 to enable thesame. Actuations of the keyboard 12 by the user and in other wordsinformation characteristic of the heating time and high frequency outputsettings is fed into the microcomputer 18, thus opening and closing therelay 19 in response to the heating time settings and switching on andoff the high voltage switch 27 in response to the high frequency outputsettings.

The output terminals 39 of the microcomputer 18 deliver the outputsignals to the display tubes 13 on the control panel 10 for the purposeof displaying the cooking output, time and modes settings.

FIG. 7 shows a flow chart drawn in conjunction with the microcomputer18. When a major class key "3" characteristic of poultry on the key pads11 is selected and then the weight keys on the key pads 11 are actuatedto key in "2.0 kg", the optimum amount of heating time and the optimumamount of high frequency output are automatically decided and autocooking operation is executed upon subsequent depression of a start key.

FIG. 8 graphically represents the contents of the ROM in themicrocomputer 18. In the example given, there are defined three weightbrackets" "0.15-0.7 kg", "0.7-1.5 kg" and "1.5-5.8 kg". These weightbrackets correspond to the actual weights of the load in the sub-classes"Cornish hen", "chicken" and "turkey" in the case of poultry. Forexample, "Cornish hen" which is widely used in home cooking falls withina weight range of "0.15 to 0.7 kg". The optimum heating conditions foreach of these weight brackets are established by heating outputs W₁, W₂,. . . W₅ (in watts) and constants a₁, a₁₂, . . . a₅₃ and b₁, b₁₂, . . .b₅₂ which define heating time slots T₁, T₂, . . . T₅. In the case ofbeef, major class No. 1 and pork, major class No. 2 different frompoultry having the sub-classes, the same results of cooking are equallyavailable from the same program relying upon establishment of the weightbrackets as taught in the above embodiment.

FIG. 9 typically shows the relationship among the weight of poultry,heating output and heating time, in which heating is effected with aheating time as determined by a graph plotted with a straight line inzone "a" and 700 watts of output when weight is inputted within a rangeof "0.15 to 0.7 kg".

                                      TABLE                                       __________________________________________________________________________                Automatically-decided                                                         item                                                              Input item  High                  Zone                                        Major                                                                              Weight frequency     Corresponding                                                                         in                                          class                                                                              kg     output W                                                                            Heating time                                                                          sub-class                                                                             FIG. 5                                      __________________________________________________________________________    Poultry                                                                             0.15-0.7                                                                             700  2'20"-10'53"                                                                          Cornish hen                                                                           (a)                                              0.7-1.5                                                                              700   9'20"-20'                                                                             Chicken (b)                                              1.5-5.8                                                                              490   16'40"-64'27"                                                                         Turkey  (c)                                         __________________________________________________________________________

In this manner, satisfactory auto cooking is expected only when the userselects one of the major class selection keys and input the actualweight of the load.

As is clear from the foregoing, the high frequency heating applianceembodying the present invention applicable as microwave ovens for homeor business use is adapted such that it performs automaticdeterminations as to high frequency output and heating time if the kind(major class) and the actual weight of the heating load are keyed in.Advantageously, the present appliance provides convenience for theuser's use, simplicity of the stored program in the microcomputer,minimum numbers of steps to be stored in the ROM and RAM andcorresponding decreases in the capacities of the ROM and RAM.

We claim:
 1. A high frequency heating apparatus comprising a heatingcompartment to keep food to be heated, a high frequency oscillator forheating the food by radiating high frequency waves into said heatingcompartment, a control circuit unit possessing a program function andcontaining a microcomputer for controlling an output of high frequencyoscillator, selection keys for selecting a major classification of thefood and for feeding this classification information into said controlcircuit unit, and a weight key for feeding the weight of the food intosaid control circuit unit, wherein said control circuit unit includes adetermination means for determining a minor classification of the foodbased on the major classification of the food from said selection keysand the weight of the food from said weight key and also includes asetting means for setting the output of the waves from said oscillatorand a heating time T based on the minor classification from thedetermination means and the weight from said weight key, and whereinsaid heating time T is determined from the following formula, assumingthat the constants set in accordance with the minor classification fromsaid determination means are a and b and the weight of the food is W:

    T=a+bW.


2. A high frequency heating apparatus as set forth in claim 1, wherein,when the major classification of food is poultry, the minorclassifications are Cornish hen, chicken, and turkey according to theweight class, and the high frequency output and heating time aredetermined for each minor classification.